________ is used to identify changes in the blood vessels in the eye and to diagnose systemic diseases.

A) Exophthalmometry
B) Gonioscopy
C) Ophthalmoscopy
D) Tonometry

Ophthalmoscopy is a diagnostic test used to examine the inside of the eye, specifically the optic nerve, retina, and blood vessels. This test can help identify changes and abnormalities in the blood vessels that could indicate systemic diseases, such as hypertension and diabetes. Exophthalmometry measures the protrusion of the eyeball from the socket, gonioscopy assesses the drainage angle of the eye, and tonometry measures intraocular pressure.